The dynamic evolution and interaction with dielectric material of the discharge in packed bed reactor

Abstract

In this paper, dielectric columns with different dielectric constants are employed as dielectric materials in the packed bed reactor to investigate the dynamic behaviors of plasma interaction processes. The effects of the dielectric constants (zirconia: ε = 25 and PTFE: ε = 2.5) on the production of reactive species are studied for plasma catalysis applications. Comparison studies of discharge images, electrical characteristics, discharge dynamic evolution and spatial-temporal resolved optical emission spectroscopy are carried on when zirconia and PTFE columns are employed. The results show that there are four discharge processes existing in the packed bed reactor: surface streamer on the dielectric column, local discharge at the contact point, surface discharge on the grounded dielectric plate, and the volume discharge. The production of reactive species such as N 2 (C 3 Π u ), N + 2 (B 2 Σ + u ) and O(3p 5 P) depend on the discharge processes to a great extent. The production of the N + 2 (B 2 Σ + u ) always accompanies the formation of the streamer by electrons direct impact process to excite the ground state nitrogen molecules to N + 2 (B 2 Σ + u ). The O(3p 5 P) is generated in two different ways, which plays a major role during the voltage pulse raising and falling time, respectively. The rst way is the direct and fast one-step ionization and excitation by high energy electrons with O 2 . The second way is the energy transfer from the nitrogen metastable N 2 (A 3 Σ + u ) and energetic electrons, in which the O is rst ionized from O 2 and then excited to O(3p 5 P). Furthermore, compared with a zirconia column, a PTFE column is more conductive to the generation of reactive species.

Reduced electric field and gas temperature effects on chemical product dynamics in air surface dielectric barrier discharges: from macro-physical parameters to micro-chemical mechanisms

“…The reduced electric field E/n could be assessed by the intensity ratio of the second positive system (SPS) to the first negative system (FNS) of N 2 . SPS and FNS bands 35,36 correspond to the transitions N 2 (C 3 Π u , v = 0) → N 2 (B 3 Π g , v = 0) and N 2 + (B 2 Σ g + , v = 0) → N 2 + (X 2 Σ g + , v = 0), respectively. The wavelengths of these band heads are 337.1 nm and 391.4 nm.…”

Degradation of Benzene Using Dielectric Barrier Discharge Plasma Combined with Transition Metal Oxide Catalyst in Air

“…One of the reasons for this is that the catalyst decreases the discharge gap and increases the reduced electric filed E/N due to the reductions in the gas molecules, thus reducing the breakdown voltage [22]. Furthermore, charge accumulates on the surfaces of the catalysts, and the electric field is stronger at the contact points between catalyst particles and between the catalyst and the DBD reactor tubes, which makes it easier to discharge [23]. In DBD, the gas is broken down at a random location when the applied elec is larger than the gas breakdown electric field.…”

“…The process of forming O 3p 5 P is as follows: [23] e + O 2 ⟶ e + O P 3 + O S 1 , log k =-8.8-11.9/Θ (6)…”

Promoting volatile organic compounds removal by a magnetically assisted nanosecond pulsed gear‐cylinder dielectric barrier discharge

“…[44] Besides, as a critical oxidative species in contamination treatment, OH (A-X, 309.7 nm) can also be detected in the presented work (Figure 8b). [45][46][47] It is also clear that both N 2 (C-B) and OH(A-X) in the gear-cylinder DBD plasma are promoted by applying the magnetic field, which is beneficial to enhance the degradation effect of toluene by plasma. [48] The emission spectra of N 2 (C-B) are also used to determine the rotational temperature (T rot ) and vibrational temperature (T vib ) of the second positive system of N 2 without and with the magnetic field by fitting the experimental spectra with the simulated ones using SPECAIR software.…”